How to understand the `gpg failed to sign the data` problem in git

README.md

Problem

You have installed GPG, then tried to commit and suddenly you see this error message after it:

error: gpg failed to sign the data
fatal: failed to write commit object

Debug

For understanding what's going on, first check what git is doing, so add GIT_TRACE=1 at the beginning of the command you used before (git commit or git rebase):

GIT_TRACE=1 git commit

With that you can see what GPG is doing: Probably you will see something like this

10:37:22.346480 run-command.c:637       trace: run_command: gpg --status-fd=2 -bsau <your GPG key>

(Check if your GPG key is correct)

Execute that gpg command again in the command line:

gpg --status-fd=2 -bsau <your GPG key>

👆🏻 With this now you could see what happened in detail!

Solutions

We can have many problems, but I list what I found:

1. It could be that the GPG key was expired: https://stackoverflow.com/a/47561300/532912

2. Another thing could be that the secret key was not set properly (In my case the message said gpg: signing failed: No secret key as it can be see in the image below). It means that is not finding the key that was set. You would need to set up the GPG key in Git (again):

   • List the secret keys available in GPG.

   gpg --list-secret-keys --keyid-format=long

   • Copy your key
   • Set your key for your user in git

   git config --global user.signingkey <your key>

3. Another popular solution that could help was shared here by @NirajanMahara: https://gist.github.com/paolocarrasco/18ca8fe6e63490ae1be23e84a7039374?permalink_comment_id=3767413#gistcomment-3767413

4. You can see in the thread of this gist other ways to find the solution to other problems. I recommend to read the Github guide for signing commits with GPG.

Hope it helps!

I'm on Ubuntu, Thanks @NirajanMahara ,It's worked for me 👍

On MacOS, I have to install pinentry-mac to enter passphrase

brew install pinentry-mac
echo "pinentry-program $(which pinentry-mac)" >> ~/.gnupg/gpg-agent.conf
killall gpg-agent

Thank you!

My issue was that I had added the PGP key with my email, while my commits on the repo were signed with my GitHub-provided noreply email address.

To solve this issue, I had to run gpg --edit-key [your key] followed by gpg> adduid to add the second email address.

https://docs.github.com/en/authentication/managing-commit-signature-verification/associating-an-email-with-your-gpg-key

This worked for me! Thanks

On MacOS, I have to install pinentry-mac to enter passphrase

brew install pinentry-mac
echo "pinentry-program $(which pinentry-mac)" >> ~/.gnupg/gpg-agent.conf
killall gpg-agent

This is the true solution 👍

This worked for me as well. Thanks @bdangeb6tp !!